This application claims the benefit of Korean Patent Application No. 1999-40815, filed on Sep. 21, 1999, which is hereby incorporated by reference for all purposes as if fully set forth herein.
1. Field of the Invention
The present invention relates to a liquid crystal display, and more particularly to a liquid crystal display device that is adapted to reduce flicker.
2. Discussion of the Related Art
Generally, a liquid crystal display (LCD) includes a liquid crystal panel and drive circuitry for driving the liquid crystal panel. A lower substrate of the liquid crystal panel is provided with switching devices (i.e., a thin film transistor array) for individually switching signals applied to liquid crystal cells. A gate terminal of the switching device is connected to a gate driver while a source terminal thereof is connected to a source driver. A drain terminal of the switching device is connected to a pixel electrode. A common voltage Vcom is applied to a common electrode of an upper electrode of the liquid crystal panel. Liquid crystal cells arranged in a matrix type are provided between the upper substrate and the lower substrate.
The gate driver applies a scanning signal sequentially to each gate line under control of the driving circuit. The source driver applies an image signal to each data line under control of the driving circuit. When an image signal is applied to a thin film transistor (TFT) turned on by a scanning signal, the image signal moves through the source terminal and the drain terminal onto a pixel electrode. At this time, the orientation of a liquid crystal cell is controlled by a voltage difference between an ITO (indium-tin-oxide) film supplied with the common voltage Vcom and the pixel electrode supplied with an image signal.
Referring to FIG. 1, a conventional LCD includes an ITO film 20 supplied with a common voltage Vcom from a common voltage generator 30 via Ag dots 12 provided on a lower substrate 10. Conductive patterns 14 are provided between the Ag dots 12. The liquid crystal panel is usually provided with at least two common voltage lines as shown in FIG. 1. The Ag dots 12 typically have a spherical shape, are conductive, and are provided at locations A, B, C and D position on the lower substrate 10. The ITO film 20 is arranged on the upper portion so as to apply the common voltage over the display. The common voltage Vcom applied from the common voltage generator 30 to the liquid crystal panel is delivered, via the Ag dots 12, to the ITO film 20.
Assuming that the conductive pattern linking the C position with the D position, hereinafter referred to as xe2x80x9cC-D linexe2x80x9d, makes an X axis, the level of the common voltage Vcom applied to the X axis is shown in FIG. 2A. Also, assuming that the conductive patternn linking the A position with the B position, hereinafter referred to as xe2x80x9cA-B linexe2x80x9d, makes a Y axis, the level of the common voltage Vcom applied to the Y axis is shown in FIG. 2B. As can seen from FIG. 2A and FIG. 2B, the common voltages applied from the common voltage generator 30 to the X and Y axes of the lower substrate 10 are the same. When the ITO film 20 has a low resistance, a common voltage having a uniform level is formed across the entire panel. However, signals from gate driving integrated circuits (IC""s) and from source driving IC""s of the data driver have line delays caused by wire resistance and parasitic capacitance. More specifically, scanning signals from gate driving IC""s and data signals from source driving IC""s encounter a wire resistance that depends on the shape of the conductive pattern 14, its material, length, width and thickness. Also, said signals are impacted by the capacitances of the gate electrodes, the capacitance between the electrodes of the liquid crystal cell, the capacitance value between the conductive pattern 14 and the data signal wire and a stray capacitance around the conductive pattern that form a parasitic capacitor. For this reason, electric charges in pixel cells located at the A and B positions can be different enough to cause flicker. Also, since the common voltage Vcom is applied independently of the charge and discharge characteristics of each part of the liquid crystal display panel, the extent of the flicker is different at each part of the liquid crystal display panel. If the flicker is serious, then it becomes difficult to determine an appropriate level of the common voltage Vcom.
Accordingly, the present invention is directed to a liquid crystal display device that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a liquid crystal display device that has reduced flicker.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a liquid crystal display device according to an embodiment of the present invention includes a common voltage delivering means being formed into a spherical shape on a lower substrate to deliver a common voltage to an upper substrate; a plurality of link points being formed between the common voltage delivering means to deliver the common voltage to a transparent electrode film; and a plurality of links provided between the link points to have a different resistance value.
A liquid crystal display device according to another embodiment of the present invention includes common voltage delivering means being formed into a spherical shape on a lower substrate to deliver a common voltage to an upper substrate; a plurality of link points being formed into a slot shape between the common voltage delivering means to deliver the common voltage to a transparent electrode film; and a plurality of links formed in a slot shape in vicinity of the respective link points to have a different resistance value.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.